Robot fish changes direction with a quick tail wiggle

A new flexible robotic fish can quickly change direction just by wiggling its tail, closely mimicking the behaviour of real fish. Developed by Andrew Marchese from the Massachusetts Institute of Technology and colleagues, it's the first soft-bodied robot with an onboard power source that can move its body at high speed.

Made of silicone rubber, the robot's brain is protected by a rigid head while its belly is filled with carbon dioxide. Releasing the gas into different parts of the pliable tail inflates actuators, allowing the fish to undulate. "It's similar to blowing up a balloon," says Marchese.

The robo-fish's movement can be controlled wirelessly – how long the actuators are inflated for is responsible for the angle of the tail, while the nozzle diameter determines its speed. The two factors are controlled separately, just like a real fish, although it wasn't an intentional design feature.

While rigid designs are programmed to avoid collisions and prevent damage, bumping into obstacles can help this robot reach its destination. "The manoeuvre is so fast and it's got such high body curvature that it shows that soft robots may be more capable than hard robots in some tasks," says Marchese.

The team thinks the robot could be used to infiltrate schools of fish to gather information about their behaviour. However they will need to improve its longevity: a carbon dioxide canister can only power about 30 manoeuvres before it runs out. A new version that pumps water instead can sustain the fish for up to 30 minutes.

The research group has already developed a soft robotic snake that can crawl autonomously powered by air, reaching a leisurely top speed of 19 millimetres per second.

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